The present disclosure relates to fiber matrix intermediates (also known as “rovings”) and a method for their manufacture. The disclosure is directed in particular to fiber matrix intermediates for the manufacture of fiber composites with a thermoplastic matrix. Products made from these can be e.g., organic sheets that are employed today primarily in automobile and aircraft construction. Further potentials exist in the production of front ends, seats, carriers and pedals.
Organic sheets are fiber matrix intermediates. They consist of a woven fabric or scrim made from continuous fibers, embedded in a thermoplastic matrix. The advantages of a thermoplastic matrix lie in the high automation potential, such as the continuous production and the hot formability of the intermediates, and the resulting short process times compared to conventional thermoset fiber composites. This is of great interest particularly in the automotive industry with its short process times. Fiber materials frequently used here are glass, basalt aramid and carbon. In woven fabrics and scrims, the fibers can also run at right-angles to one another so that the mechanical properties such as rigidity, strength and thermal expansion can be better defined than for their metallic archetypes. In contrast to metal sheets, the tensile and compressive behavior is not symmetrical.
The high-strength thermoplastic fiber composites are generally produced by a bundle of continuous filaments, such as carbon fibers, basalt aramid fibers or glass fibers, first being laid up as reinforcing fibers. A size of matrix material consisting of a thermoplastic adhesive material—such as polyamide resins, aromatic polyamides, thermoplastic polyurethane or polyester—is then applied over and/or under the reinforcing fibers. The matrix material is then melted by the application of heat and possibly pressure in order to obtain the fiber composite. A method of this type is disclosed for example in WO 2005/033390 A2.
Matrix materials of cross-linkable materials and similar materials are naturally also common and generally known per se to a person skilled in the art.
Hybrid fiber composites can also be used as organic sheets, in which, in addition to the reinforcing filaments, further filaments are also inserted to serve as matrix material. The filaments are preferably oriented unidirectionally; this can be achieved e.g., by separating the filaments using suitable guiding devices and yarn guiding units. Here again, a matrix material or fixing agent is finally applied in order to produce the composite thermally or chemically.
The state-of-the-art methods for production of the hybrid fiber composites have the disadvantage that a uniform application of the matrix material is sometimes difficult to achieve. Furthermore, different types of filaments frequently have to be separated or spread, and with the different mechanical properties of these filaments, this can lead to problems.